Endless belt conveyors made from a fabric carcass such as nylon, polyester, kevlar, fiberglass, steel, monofilament etc. and covered with a rubber compound and/or urethane PVC from 1/16" to over 1" thick are used to convey many types of raw and processed materials in many environmental conditions. As a result, many factors such as temperature, moisture, loading characteristics, design characteristics and wind forces cause problems keeping the conveyor belt aligned on both the troughing (carrying side) and the return side of the belt. The misalignment of the belt causes damage to the belt, damage to the structure carrying the belt, and spillage problems.
Typically, the training rollers utilized to monitor and return the belt to proper alignment have been mounted below the belt where the residue adhering to the carrying surface of the belt can transfer to the training roller causing inaccurate alignment. Additionally, the only force acting directly on the trainer is the weight of the conveyor belt. Typically other types of training idlers are pivoted from a center gudgeon and have guide rollers mounted several inches from the edge of the belt so that the belt has to move considerably out of alignment to cause actuation of the training idler or the pivot was mounted for universal angular movement and contact with a braking mechanism caused the idler to be displaced in a direction to restore the belt to alignment. The center gudgeon builds up with material from the dirty side of the belt causing it to "freeze" in place or just "jam" itself from working properly.